1. Field of the Invention
The present invention relates to inspecting walls of tanks, vessels and the like. More particularly, the present invention relates to an inspection vehicle, for use with a deployment unit, that moves along and inspects vessel walls. The United States Government has rights in this invention pursuant to Contract No. DE-AC09-89SR18035 between the U.S. Department of Energy and Westinghouse Savannah River Company.
2. Discussion of Background
The use of probes for inspecting pipelines, tanks, vessel surfaces and the like is well known in the art. Many U.S. patents disclose pipe crawlers and other similar vehicles used to inspect piping surfaces or vessel and tank walls. Inspection devices mounted on these vehicles include ultrasonic probes and eddy current probes that collect inspection information for later analysis or relay such information periodically to a unit located outside of the vessel or pipeline being inspected.
For example, in U.S. Pat. No. 5,025,215, Pirl describes a helically-driven device having a combination eddy current and ultrasonic testing probe attached thereto. The device features a head assembly that is fixable to the surface of the tubing by a pressure bladder, which is supplied fluid by a conduit system. The head assembly is connected to a drive motor located on an external drive frame assembly by a coaxial conduit.
Metala et al, in U.S. Pat. No. 4,856,337, discloses an inspecting apparatus in the form of a cylindrical housing assembly insertable within a tube or piping. A probe carrier, holding an eddy current probe and a plurality of ultrasonic probes, is rotatably mountable within the housing assembly and helically movable with respect to the housing.
An apparatus for traveling through piping is disclosed in U.S. Pat. No. 4,770,105, issued to Takagi et al. The apparatus features a plurality of continuous treads that are spring-biased to keep the apparatus in contact with the inner wall of the piping being inspected. The treads are driven by motors operating through transmission gearing.
Other related devices include Fluornoy (U.S. Pat. No. 4,418,574) and Beaver et al (U.S. Pat. No. 3,949,292). Fluornoy discloses a method and device for measuring wall thickness using a magnetic reluctance coil. Beaver et al disclose a pivoting inspection structure that is urged against the interior wall of piping by spring-loaded vanes.
Still another related device is the vessel examination system disclosed in U.S. Pat. No. 3,988,922 by Clark et al. The system features a remotely-controlled, instrument-carrying vehicle with motor-driven magnetic wheels to propel the vehicle along the interior surface of the vessel being inspected. For remote location determination, the vehicle uses an ultrasonic signal system employing a triangulation technique.
Despite the abundance of probe-carrying devices for piping, vessel walls and the like, it is believed that no inspection device provides continuous location and mapping capabilities and has sufficient holding power against the wall being inspected, yet is small enough to pass through piping having a diameter less than approximately 8 inches. Furthermore, it is believed that no existing inspection devices can be maneuvered sufficiently through limited-access vessels, such as underground piping or tanks.